Process for the production of lightcolored,color-stable fatty acids

ABSTRACT

LIGHT-COLORED, COLOR-STABLE FATTY ACIDS OF 8-18 CARBON ATOMS ARE PRODUCED BY HEATING THE CRUDE FATTY ACIDS IN THE PRESENCE OF VANADIUM OXIDE, A LOWER ALKYL VANADATE, A LOWER ALKYL ESTER OF ZIRCONIC ACID, AN AROMATIC CARBOXYLIC ACID OR LOWER ALKYL ESTER THEREOF, OR A MIXTURE OF THE AROMATIC CARBOXYLIC ACID OR ESTER WITH THE ALKYL ESTER OF TITANIC OR ZIRCONIC ACID AT ABOUT 180*-260*C., AND THEN DISTILLING, THE RESULTING MIXTURE UNDER A VACUUM.

nited States Patent 3,833,629 PROCESS FOR THE PRODUCTION OF LIGHT- COLORED, COLOR-STABLE FATTY ACIDS Sasanka Sekhar Naskar and Gustav Renckhotf, WItten (Ruhr), Germany, assignors to Dynamit Nobel Aktrengesellschaft, Troisdorf, Germany N0 Drawing. Filed Mar. 1, 1971, Ser. No. 119,826

Int. Cl. C08h 17/36 US. Cl. 260-419 15 Claims ABSTRACT OF THE DISCLOSURE Light-colored, color-stable fatty acids of 8-18 carbon atoms are produced by heating the crude fatty acids in the presence of vanadium oxide, a lower alkyl vanadate, a lower alkyl ester of zirconic acid, an aromatic carboxylic acid or lower alkyl ester thereof, or a mixture of the aromatic carboxylic acid or ester with the alkyl ester of titanic or zirconic acid at about l80260 C., and then distilling, the resulting mixture under a vacuum.

This invention relates to a process for the production of light-colored, color-stable fatty acids of a chain length of C -C The process is characterized in that crude fatty acids or mixtures thereof are heated with vanadium oxide or an alkyl vanadate, or with alkyl esters of zirconic acid, or also with certain aromatic carboxylic acids or the alkyl esters thereof, or with these aromatic carboxylic acids or the alkyl esters thereof in the presence of alkyl esters of titanic or zirconic acid, and a vacuum distillation is conducted thereafter.

It is known that inorganic and Organic boron compounds are employed for improving the color of fatty acids. US. Pat. 2,583,028 and British Pat. 1,081,522 describe a process for the treatment of fatty acids with boron trifluoride or the ether complex thereof. However, this process is connected with considerable corrosion problems. According to US. Pat. 2,862,943 or DAS (German Published Application) l,2l4,212, the fatty acids are treated with inorganic or organic boron compounds. The disadvantages of this process reside in that the oxygencontaining boron compounds have the effect of a condensation catalyst, and promote the formation of nonsaponifiable condensation products of the fatty acid, which products remain in the residue after the distillation of the treated fatty acids, as a non-saponifiable, non-distillable compound, and are thus lost. In DAS 1,073,665, a process is even described relating to the preparation of precisely these condensation products from fatty acids, wherein oxygen-containing boron compounds are employed as the condensation catalyst. The yield in non-saponifiable condensation products is up to 92% in this process.

A possibility for a process has now been discovered for the production of lightfast fatty acids of the chain length of C C or mixtures thereof, which does not exhibit the disadvantages of the processes employed heretofore. The process resides in that the crude fatty acids are heated with 01-06% by weight, preferably 02-03% by weight of vanadium oxide or of an alkyl vanadate of 1-4 carbon atoms in the alkyl residue for a period of 0.5-4 hours, preferably l-3 hours, to temperatures of 180-260 0., preferably ZOO-245 C. under normal pressure, optionally under a slight vacuum of up to 500 torr (mm. Hg); or with 0.l-1.0% by weight, preferably 0.2- 0.6% by weight, of an alkyl ester of zirconic acid of 1-6 carbon atoms in the alkyl residue for a period of 0.5-4 hours, preferably 1-3 hours, to temperatures of ISO-250 0, preferably 200-240" C. under normal pressure, optionally under a slight vacuum; or also with 0.1-0.2% by weight of an aromatic carboxylic acid or the esters thereof of the general formula Ar(COOR) wherein x is 1-4, Ar represents an aryl residue or an alkylaryl residue, and R is hydrogen or an alkyl residue of 1-4 carbon atoms; or with the above-mentioned aromatic carboxylic acids or the esters thereof with the simultaneous presence of 01-05% by weight of an alkyl ester of titanic or zirconic acid of 1-8 carbon atoms in the alkyl group, for a period of 0.5-8 hours, preferably l-4 hours, to 180-260 0., preferably ZOO-250 C. under normal pressure, optionally under a slight vacuum; and then a vacuum distillation is conducted.

When working, according to this invention, with the vanadium compound or with the alkyl ester of zirconic acid, the vanadium compounds remain bound to the impurities present in the fatty acid in the distillation residue after the treatment. The process exhibits the advantage that even after the treatment with vanadium oxide or an alkyl vanadate and subsequent distillation, the distillate thus obtained does not contain quantitatively any larger amounts'of non-saponifiable compounds than are contained in the distillate of the untreated fatty acids. In particular, the distillation residue of the thus-treated fatty acid does not contain any newly formed condensation products, as is the case in the treatment with boric acid or the esters thereof, inasmuch as boron compounds have the effect of Lewis catalysts and promote the production of non-saponifiable, non-distillable condensation products. In the process of this invention, after the distillation is finished, not readily distillable vanadium compounds or zirconium compounds are found in the distillation residue.

When the product is conducted With the aromatic carboxylic acids or the esters thereof to be employed according to this invention, the treatment time is dependent on the treatment temperature: about 2-3 hours at 240-250 C.; about 4-5 hours at 220-230" 0.; about 6-8 hours at ZOO-210 C.

In this connection, the amount of the treatment reactants is dependent on the type and quality of the crude fatty acid or the crude fatty acid mixtures. For C -C fatty acids stemming from palm nut oil or coconut oil and being extremely sensitive to light and heat, it is possible to add 01-02% of aromatic carboxylic acid or the lower alkyl ester thereof and 01-02% of alkyl esters of titanic or zirconic acid; for C -C fatty acids, sufiicient amounts are 0.05-0.1% of aromatic carboxylic acid or the lower alkyl esters thereof and 01-05% of alkyl esters of titanic or zirconic acid.

In the mode of operation according to this invention, the aromatic carboxylic acids and the titanic or zirconic acid remain bound to the impurities present in the fatty acid, in the distillation residue.

In the discontinuous distillation, the sump temperature and the concentration of the treatment medium are increased. Sump temperatures which are too high and distillation times which are too long can have the result that the thus-bound impurities are split again, and the quality of the distillate is impaired accordingly. Besides, there is the danger that the aromatic carboxylic acids are distilled together with the fatty acid. For this reason, it is necessary, especially in case of long-chain fatty acids,

to conduct the distillation under a vacuum of at least 1-2 torr.

The process of the present invention exhibits the ad vantage that the distillate does not contain any greater amounts of non-saponifiable impurities than the distillate of the untreated fatty acids, even after the treatment with the aromatic carboxylic acids or the lower alkyl esters thereof, or after the treatment with the aromatic carboxylic acids or the alkyl esters thereof in the presence of the alkyl esters of titanic or zirconic acid and after the subsequent distillation.

A special advantage of the present process resides in that the distillation residue of the thus-treated fatty acid does not contain any newly formed condensation products, as is the case in the treatment with boric acid or the esters thereof. The boron compounds, which have the effect of Lewis catalysts, promote the formation of nonsaponifiable, non-distillable condensation products. After,

the distillation has been terminated, high-boiling carbox-' ylic acid derivatives and non-distillable titanic or zirconic acid compounds are present in the distillation residue.

The aromatic carboxylic acids to be employed accord ing to this invention can be mono-, di-, tri-, and tetracarboxylic acids, e.g. benzoic acid, toluic acid, all phthalic acids, trimellitic and pyromellitic acid or the lower alkyl esters thereof, for example, dimethyl terephthalate, di methyl isophthalate, etc. Benzoic acid, toluic acid, and orthophthalic acid are only suitable for the treatment of the C -C fatty acids. A treatment of the C -C fatty acids with terephthalic acid, trimellitic acid, dimethyl terephthalate, and dimethyl isophthalate results in an advantageous effect on lightfastness and thermal stability. For C14-C13 fatty acids, only isophthalic acid, trirnellitic acid, or pyromellitic acid are to be employed. The boiling point of the added carboxylic acid or the alkyl ester thereof is below the boiling point of the fatty acids.

According to the present invention, the treatment of the fatty acids for purposes of color stabilization can be conducted with aromatic monoor polycarboxylic acids or the alkyl esters thereof. However, a treatment with aromatic carboxylic acids or the lower alkyl esters thereof in the presence of alkyl esters of titanic or zirconic acid results in an optimum effect with respect to the lightfastness or thermal stability and the lightness of the distilled fatty acids.

The source for the crude fatty acids can be natural fats and oils, as well as synthetic fatty acids. A large portion of these fatty acids is produced as by-products during various stages of the refinery of edible oils and fats, for example during the deacidification by neutralization with an alkali, or during the direct distillation of edible oils and fats of a higher free acid content under vacuum, decolorization and deodorization.

During the treatment of the deslimed or crude oil with alkali, the free fatty acids are converted into soaps and separated. The thus-obtained soap stock contains, in addition to neutral oil, also slimy substances and other impurities. The soap stock is split by means of a dilute mineral acid, and the thus-produced refined fatty acid, also called edible oil (60-80% free fatty acid) is split under pressure in an autoclave in the presence of water. The fatty acid split off during this step is obtained by distillation and treated according to the present invention and once more distilled under vacuum.

In case of a fat or oil exhibiting a poor color quality and a high acid content, it is possible to make do without any refining procedure, if the fat or oil is split directly and the thus-produced fatty acid is treated according to this invention and distilled.

The processes of this invention can be conducted in a discontinuous as well as continuous manner.

The demands regarding the quality of fatty acids for the production of soap, cosmetics, lubricants, and the like have risen to such an extent that a considerable advance in the art is to be attributed to the treatment of this invention conducted on color-unstable fatty acids from tech: nical oils and fats, which leads to lightfast and thermally stable acids.

The color stability of the fatty acid forerunnings treated according to the invention and those which are untreated was determined by the heating of samples in a glass tube having a diameter of 14 mm. and a filling level of mm., to 200 C. during a period of 6 hours. This heating test was conducted in a drying chamber equipped with a thermostat, which chamber was not opened during the entire duration of the test. The test tubes were in each case covered by a cap. The color intensity was measured in iodine color number units, wherein the iodine color number indicates how many milligrams of free iodine are contained in 100 milliliters of aqueous iodine-potassium iodide solution at the same color depth, measuring at a layer thickness of 25 millimeters.

The iodine color number and the hazen unit were measured in a 'Lovibond 1000 comparator and accessories, made by Tintometer.

The effect attainable in the treatment of fatty acids according to the present invention can be seen from the examples set forth below.

The following are examples for the treatment of the crude fatty acids with zirconic acid esters according to this invention:

EXAMPLE 1 (a) 1200 parts by weight of crude coconut oil fatty acid, obtained by splitting refined fatty acid (also called edible oil) under pressure, which refined fatty acid was produced as a by-product during the neutralization of the crude coconut oil with solution of sodium hydroxide, was distilled without additives under vacuum (l2 torr) within about 2 hours over a small column. A small amount of forerunnings and a main fraction were withdrawn.

(b) 1200 parts by weight of the crude coconut oil fatty acid described under (a) was dewatered under agitation and mixed, at a sump temperature of 180 C., with 0.4% by weight of zirconic acid butylate. The treatment time was 2 hours. During this period, a temperature of 240 C. was maintained. Then, the sump temperature was cooled to 90 C. and the content of the flask was distilled under vacuum (1-2 torr) over a small distillation column within about 2 hours. A small amount of forerunnings and a main fraction were withdrawn.

(a) 1200 parts by weight of crude palm nut oil fatty acid, obtained by splitting crude palm nut oil under pressure, was distilled without additives under vacuum (1-2 torr) within about 2 hours over a small column. A small amount of a forerun and a main fraction were withdrawn.

(b) 1200 parts by weight of the crude palm nut oil fatty acid described under (a) was dewatered under agitation and mixed, at a sump temperature of 180 C., with 0.5% by weight of the propyl ester of zirconic acid; the mixture was then treated and distilled as set forth in Example (a) 1200 parts by weight of a crude fatty acid of 20% palm oil, 20% coconut oil, and 60% tallow fatty acid was distilled without additives under vacuum (1 torr) within about 2 hours over a small column. A small forerun and a main fraction were removed.

(b) 1200 parts by weight of the crude fatty acid described under (a) was dewatered under agitation and at 700 torr and 180 0., mixed with 0.5% of zirconium acetylacetonate, and treated for 2.5 hours at 240 C. and

In Examples 2, 4, 6, 8, and 10 of the table, respectively 1200 parts by weight of the anhydrous fatty acid was heated with the addition of vanadic acid anhydride or the alkyl ester of vanadic acid for a period of 2-3 hours to a temperature of 230-245 C. Thereupon, the temperature was lowered to 90 C. by cooling, and the thustreated fatty acids were distilled under a vacuum of 1-2 torr over a small distillation column within 2 hours; a small forerun (about 1-2%) and a main fraction (about 91-94%) were withdrawn. The forerun from most of the treated technical fatty acids exhibits a strongly unpleasant odor and is not utilized. Therefore, no heating test was conducted, either. The residue was about 48%. The nonsaponifiable substance in the residue was determined. In connection with the main run of the untreated and treated fatty acids, the hazen unit of freshly distilled samples and the iodine color number after heating the sample at 200 C. for 6 hours were determined. The iodine color number and the hazen unit were measured in the Lovibond 1000 comparator and the accessories thereof, by Tintometer.

TABLE 1 Main fraction Backflow Treatment Iodine Forerun, Percent Color color No. Percent U.V., Ex. Type of Fatty Time Temp. percent y Acid Hazen after 6 by per No. fatty acid acid cut Agent (hr.) C.) by weight weight N 0. unit hr./200 0. weight cent C count.-- Ca-Ci 1. 9 93. 9 366 100-125 50 4. 2 1. 1 do C3-C1: Vanadium pentox'ido, 0.4%.. 2 240 1. 8 93. 4 367 10-15 5 4. 8 1. 2 Palm nut oil- Ca-Cm 1. 8 92. 9 360 100 50 5. 3 1. 4 do 08-010 Vanadyl butylate, 0.3%..- 3 230 1. 9 92. 5 360 20 6 5 6 1. 6 Cocunuh (In-C l. 6 91. 6 27]. 150 40 6. 8 2. 2 .....do 012-614 Vanadium pentoxide, 0.3%.. 2 245 1. 8 91. 3 270 70 8-9 6. 9 2. 4 P l nut 11 (3 -0 1. 9 90. 8 202 100-125 35 7. 3 1. 8 .do--.- Cit-Cm Vanadium (III) oxide, 0.2%-- 2 240 1. 8 90.7 202 60 8 7. 5 1. 7 ll G -C 1. 2 91. 0 197 225-250 20-25 7. 8 1. 4 .do. O a-Cu Vanadium pentoxide, 0.2%.- 2 1. 5 90. 6 197 53-9 7. 9 1, 5

700 torr; then, the mixture was cooled to 90 C. and thereafter distilled under vacuum (1 torr) over a small column within about 2 hours. A small forerun and a main fraction were withdrawn.

Forerum Mainfraction Residue a b a Amount (percent by weight).-. 3. 1 2. 9 89. 1 88.9 7.8 8. 2 Acid number 389 390 215 21 Hazen unit, at once- 250 125 225-250 50 Iodine color number after 6 hours at 200 C Non-saponitiable matter EXAMPLE 4 Forerun Main fraction Residue a b a b a b Amount (percent by weight) 3. 2 3. 3 88. 5 Acid number 215 214 198 Hazen unit, at once. 225 175 225 Iodine color number after 6 hours at 200 C 50 40 Non-saponifiable matter 0. 67 0. 68 0. 53

Examples for the treatment of the crude fatty acids with vanadium oxide andalkyl vanadate according to the present invention are set forth below:

EXAMPLES In Examples 1-10 of Table 1, below, the characteristic data for the single-distilled untreated fatty acids were compared with those of the distilled fatty acids treated according to the present invention, in connection with each of the individual types of fatty acids.

b a b The following examples describe the treatment of crude fatty acids according to this invention with aromatic carboxylic acids, as well as with carboxylic acids or the esters thereof together with alkyl esters of titanic and zirconic acid:

In the experiments described in Examples 1-20 of Table 2, below, respectively 1200 parts by Weight of the anhydrous fatty acid was heated, with the addition of the aromatic carboxylic acid or the alkyl ester thereof, under agitation to 220 C. At this temperature, the alkyl ester of titanic or zirconic acid was added (except in Example 2). The treatment time was 2-3 hours. During this time, a temperature of 240250 C. was maintained. Then, the sump temperature was lowered to 90 C. by cooling, and the thus-treated fatty acids were distilled under a vacuum of 1-2 torr over a small distillation column within 2 hours; a small forerun (3-5%) and a main fraction (88-92%) were withdrawn. The forerun from most of the treated technical fatty acids has a strongly unpleasant odor and is not employed. Thus, no heating test was conducted thereon, either. The residue amounted to 5-8%. The non-saponifiable matter of the residue was determined. From the main run of the untreated and of the treated fatty acids, the hazen units of freshly distilled samples, as well as after UV irradiation at C. for 4 hours, were determined; furthermore, the iodine color number was measured after heating the sample at 200 C. for 6 hours. The iodine color number and the hazen unit were determined in the Lovibond 1000 comparator and the accessories thereof, made by Tintometer.

For comparison purposes, 1200 parts by weight of untreated fatty acid was distilled under the same conditions (Example a). The results are listed in the table. The term fatty acid cut is understood to mean a distillation cut of the untreated technical fatty acids containing predominantly (at least 80%) fatty acids of the chain length set forth in Table 2.

TAB LE 2 Treatment Example Fatty Time Temp. Fore number acid cut Type of fatty acid Agent (hours) 0.) run 1a. Cg-Cm Coconut- 4.5 C -C1 do 0.2% terephthalic acid 2 240 4. 6 (Jr-Om .do 0.2% benzoic acid, 0.1% butyl zirconate... 2 240 4. 8 G 5-01 -do 0.1% phthalic acid. 0.1% butyl zirconate 2 240 3. 3 05-01 d 0.1% dimethyl terephthalate, 0.1% butyl tltanatan- 2 240 3. 9 Ca-Cm Palm nut 011 3. 8 Ca-Cin -do 1% trimellitic acid, 0.1% ethyl titanate 4. 2 08-01: Coconut 3. 2 -01: do 1% terephthalic acid, 0.1% butyl airconate 3. 7 012-014 do 3. 7 012-014 do 0.1% dimethyl terephthalato, 0.1% butyl zrrconate- 3. s 012-011 60% tallow, 20% coconut, 20% palm oil 4. 4 0 2-01; do 0.2% isophthalic acid, 0.2% butyl titanate 2. 5 250 4. 0 Cu Soy oil- 8 0 do 3. 9 C o-C19 0013170118000 011.... 4. 9 CirCrs -.-d0--..-- 5. 1 G Oleic acid 3. 0 C15 o 2% dimethyl isophthalate, 0.2% butyl titanate 4. 0

TABLE 2.SECOND PA RT Main run Residue Percent Hazen Iodine Percent Non- Example by Acid Color after U .V. color y saponinumber weight number hazen irradiation number 1 weight hable Aiter 6 hours at 200 C.

We claim:

1. A process for the production of light-colored, colorstable fatty acids having from 8 to 18 carbon atoms and mixtures thereof which comprises heating the crude fatty acids in the presence of about 0.1 to 0.2% by weight of an aromatic carboxylic acid or the esters thereof selected from the group consisting of benzoic acid, toluic acid, the phthalic acids, trimellitic acid, pyromellitic acid, dimethyl terephthalate and dimethyl isophthalate, the boiling point of the carboxylic acid or ester thereof being below the boiling point of the fatty acids being treated at a temperature of about 200 to 250 C., for about 2 to 8 hours under normal pressure or under a slight vacuum, and thereafter distilling the resulting mixture under a vacuum.

2. The process of claim 1, wherein the crude fatty acids contain from 8 to 10 carbon atoms and the carboxylic acid is selected from the group consisting of benzoic acid, toluic acid, and ortho phthalic acid.

3. The process of claim 1, wherein the crude fatty acids contain from 8 to 12 carbon atoms and the carboxylic acids or esters are selected from the group consisting of terephthalic acid, trimellitic acid, dimethyl terephthalate, and dimcthyl isophthalate.

4. The process according to claim 1, wherein the crude fatty acid contains from 14 to 18 carbon atoms and the carboxylic acid is selected from the group consisting of isophthalic acid, trimellitic acid, and pyromellitic acid.

5. The process of claim 1, wherein the temperature is 240 to 250 C. and the amount of heating time is about 2 to 3 hours.

6. The process of claim 1, wherein the temperature is 220 to 230 C. and the amount of heating time is about 4 to 5 hours.

7. The p ocess of claim 1, wherein the temperature is 200 to 210 C. and the amount of heating time is about 6 to 8 hours.

8. A process for the production of light-colored, color stable fatty acids having from 8 to 18 carbon atoms and mixtures thereof which comprises heating thecrude fatty acids in the presence of 0.1 to 0.2% by weight of aromatic carboxylic acids and esters thereof having the general formula Ar(CO0R) wherein x is an integer from 1 to 4, Ar is phenyl or an alkyl substituted phenyl group and R is hydrogen or an alkyl group of 1 to 4 carbon atoms mixed with about 0.1 to 0.5% by Weight of alkyl esters of titanic or zirconic acid at a temperature of about 180 to 260 C. for about 0.5 to 8 hours under normal pressure or under a slight vacuum, and thereafter distilling the resulting mixture under a vacuum.

9. The process of claim 8, wherein the crude fatty acids contain 8 to 12 carbon atoms, and the amount of the alkyl esters of titanic or zirconic acid is 0.1 to 0.2%.

10. The process of claim 8, wherein the crude fatty acids contain 14 to 18 carbon atoms, the amount of the aromatic carboxylic acid is 0.05 to 0.1%, andthe amount of the alkyl esters of titanic or zirconic acid is 0.1 to 0.5%.

11. A process for the production of light-colored, color-stable fatty acids having from 8 to 18 carbon atoms and mixtures thereof which comprises heating the crude fatty acids in the presence of about 0.1 to 1.0% by weight of alkyl esters of zirconic acid having 1 to 6 carbon atoms in the alkyl group thereof, at a temperature of about to 250 C. for about 0.5 to 4 hours under normal pressure or under a slight vacuum, and thereafter distilling the resulting mixture under a vacuum.

12. The process of claim 11, wherein the crude fatty acids are heated in the presence of 0.2 to 0.6% by weight of said alkyl esters of zirconic acid at a temperature of 200 to 240 C. for about 1 to 3 hours.

13. A process for the production of light-colored, color-stable fatty acids having from 8 to 18 carbon atoms and mixtures thereof which comprises heating the crude fatty acids in the presence of about 0.1 to 0.6% by weight of a vanadium compound selected from the group consisting of alkyl vanadates having 1 to 4 carbon atoms in the alkyl group thereof at a temperature of from about 180 C. for about 0.5 to 4 hours under normal pressure or under a slight vacuum, and thereafter distilling the resulting mixture under a vacuum.

14. The process of claim 13, wherein the crude fatty acids are heated in the presence of 0.2 to 0.3% by weight of said alkyl vanadates at a temperature of 200 to 245 C. for about 1 to 3 hours.

15. The process of claim 13, wherein the slight vacuum ranges up to about 500 torr.

References Cited UNITED STATES PATENTS 3,526,649 9/1970 Naskar et a1 260-419 FOREIGN PATENTS 931,972 8/ 1955 Germany 260420 OTHER REFERENCES Chakravarty et al.: Chem. Abstracts, 1930, p. 5567. Fiiner et al.: Chem. Abstracts, vol. 45, p. 2192b.

LEWIS GOTTS, Primary Examiner 15 E. G. LOVE, Assistant Examiner 

